Effect of Age and Comedication on Levetiracetam Pharmacokinetics and Tolerability

Levetiracetam Dosing Based on Glasgow Coma Scale Scores in Pediatric Traumatic Brain Injury Patients

INTRODUCTION

 Severe traumatic brain injury (TBI) increases the risk of early posttraumatic seizures (EPTS). Guidelines suggest the use of prophylactic antiseizure agents, including levetiracetam. This study aims to evaluate the feasibility of using levetiracetam dosing based on Glasgow Comas Scale (GCS) scores with higher doses used for more severe TBI.

METHODS

 Patients 6 months to 18 years old admitted to Penn State Hershey Children's Hospital (PSHCH) with a TBI who received levetiracetam for EPTS prophylaxis with at least one documented GCS score were included. Patients were divided into two cohorts: before and after implementation of the pediatric TBI Cerner PowerPlan at PSHCH which standardized levetiracetam dosing based on GCS scores. Primary outcome was appropriate dosing of levetiracetam based on GCS. Secondary outcomes included seizure occurrence and adverse effects.

RESULTS

 Eighty-five patients were included: 42 in the pre-PowerPlan group and 43 in the post-PowerPlan group. Overall, 46 (54%) patients received the appropriate levetiracetam dose based on GCS (pre-PowerPlan, n = 19 [45%] vs. post-PowerPlan n = 27 [63%], p = 0.104). Sixty-four percent of severe TBI patients received appropriate levetiracetam dosing after implantation of the PowerPlan compared with 28% prior to the PowerPlan (p = 0.039). Three patients in each group experienced a seizure while on levetiracetam. Two patients experienced agitation and somnolence attributed to levetiracetam.

CONCLUSION

 Levetiracetam dosing based on GCS scores in pediatric TBI patients is a novel approach, and dosing accuracy may be increased with use of a PowerPlan. Additional large-scale studies are needed to evaluate efficacy and safety of this approach prior to widespread implementation.

Assessing the Incidence Rate of Neuropsychiatric Adverse Effects in Older Adults Following Levetiracetam Initiation: A Retrospective Study

Background

Levetiracetam (LEV) is commonly prescribed for epilepsy management. However, neuropsychiatric disorders (NPDs) are concerning adverse effects that may result in medication discontinuation. This study aims to examine the incidence and factors influencing LEV associated NPDs in adult patients aged 50 years and above.

Methods

A retrospective analysis was conducted on patients aged 50 years and above prescribed LEV between 2010 and 2020, with at least one follow-up appointment six months post-treatment initiation. The incidence of new-onset or aggravated NPDs and variables potentially influencing this risk were examined. Independent t-test, chi-squared, and Fisher's exact test were used, in addition to univariate and multivariate logistic regression.

Results

The study included 100 patients with a mean age at LEV start of 63.31 years (SD = 16.48). Neuropsychiatric symptoms were observed in 6 (6.0%) patients. Factors associated with new-onset NPDs were younger age at epilepsy diagnosis (p=0.005), younger age at LEV start (p=0.004), and concurrent use of Carbamazepine/Oxcarbazepine (p=0.004). On multivariate analysis, only the association with Carbamazepine/Oxcarbazepine remained significant (OR 14.62, 95% CI 1.86-114.70, p=0.011).

Conclusion

The findings indicate that the incidence of NPDs in elderly patients is relatively low (6%). Further research with larger samples is needed in comparison with a younger sample as a control group to confirm these findings.

Physiologically based pharmacokinetic modeling of levetiracetam to predict the exposure in hepatic and renal impairment and elderly populations

Levetiracetam (LEV) is an anti-epileptic drug approved for use in various populations. The pharmacokinetic (PK) behavior of LEV may be altered in the elderly and patients with renal and hepatic impairment. Thus, dosage adjustment is required. This study was conducted to investigate how the physiologically-based PK (PBPK) model describes the PKs of LEV in adult and elderly populations, as well as to predict the PKs of LEV in patients with renal and hepatic impairment in both populations. The whole-body PBPK models were developed using the reported physicochemical properties of LEV and clinical data. The models were validated using data from clinical studies with different dose ranges and different routes and intervals of administration. The fit performance of the models was assessed by comparing predicted and observed blood concentration data and PK parameters. It is recommended that the doses be reduced to ~70%, 60%, and 45% of the adult dose for the mild, moderate, and severe renal impairment populations and ~95%, 80%, and 57% of the adult dose for the Child Pugh-A (CP-A), Child Pugh-B (CP-B), and Child Pugh-C (CP-C) hepatic impairment populations, respectively. No dose adjustment is required for the healthy elderly population, but dose reduction is required for the elderly with organ dysfunction accordingly, on a scale similar to that of adults. A PBPK model of LEV was successfully developed to optimize dosing regimens for special populations.

Adverse Event Profiles of Antiseizure Medications and the Impact of Coadministration on Drug Tolerability in Adults with Epilepsy

BACKGROUND

Antiseizure medication (ASM) as monotherapy or in combination is the treatment of choice for most patients with epilepsy. Therefore, knowledge about the typical adverse events (AEs) for ASMs and other coadministered drugs (CDs) is essential for practitioners and patients. Due to frequent polypharmacy, it is often difficult to clinically assess the AE profiles of ASMs and differentiate the influence of CDs.

OBJECTIVE

This retrospective analysis aimed to determine typical AE profiles for ASMs and assess the impact of CDs on AEs in clinical practice.

METHODS

The Liverpool AE Profile (LAEP) and its domains were used to identify the AE profiles of ASMs based on data from a large German multicenter study (Epi2020). Following established classifications, drugs were grouped according to their mode of action (ASMs) or clinical indication (CDs). Bivariate correlation, multivariate ordinal regression (MORA), and artificial neural network (ANNA) analyses were performed. Bivariate correlation with Fisher's z-transformation was used to compare the correlation strength of LAEP with the Hospital Anxiety and Depression Scale (HADS) and Neurological Disorders Depression Inventory for Epilepsy (NDDI-E) to avoid LAEP bias in the context of antidepressant therapy.

RESULTS

Data from 486 patients were analyzed. The AE profiles of ASM categories and single ASMs matched those reported in the literature. Synaptic vesicle glycoprotein 2A (SV2A) and voltage-gated sodium channel (VGSC) modulators had favorable AE profiles, while brivaracetam was superior to levetiracetam regarding psychobehavioral AEs. MORA revealed that, in addition to seizure frequency, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) modulators and antidepressants were the only independent predictors of high LAEP values. After Fisher's z-transformation, correlations were significantly lower between LAEP and antidepressants than between LAEP and HADS or NDDI-E. Therefore, a bias in the results toward over interpreting the impact of antidepressants on LAEP was presumed. In the ANNA, perampanel, zonisamide, topiramate, and valproic acid were important nodes in the network, while VGSC and SV2A modulators had low relevance for predicting relevant AEs. Similarly, cardiovascular agents, analgesics, and antipsychotics were important CDs in the ANNA model.

CONCLUSION

ASMs have characteristic AE profiles that are highly reproducible and must be considered in therapeutic decision-making. Therapy using perampanel as an AMPA modulator should be considered cautiously due to its relatively high AE profile. Drugs acting via VGSCs and SV2A receptors are significantly better tolerated than other ASM categories or substances (e.g., topiramate, zonisamide, and valproate). Switching to brivaracetam is advisable in patients with psychobehavioral AEs who take levetiracetam. Because CDs frequently pharmacokinetically interact with ASMs, the cumulative AE profile must be considered.

TRIAL REGISTRATION

DRKS00022024, U1111-1252-5331.

Therapeutic drug monitoring and the therapeutic reference range of levetiracetam for Chinese patients: Problems and issues

BACKGROUND

Levetiracetam (LEV) is widely used in the clinical monotherapy or multi-drug combination treatment of seizures due to its good tolerability and efficacy. Due to a lack of large-scale clinical studies, the relationship between levetiracetam concentrations, disease activity and adverse is unclear, limiting the usefulness of therapeutic drug monitoring (TDM) based LEV plasma levels. This study was intended to investigate factors influencing the pharmacokinetics of and the appropriate reference range of LEV concentration using available LEV TDM data.

METHODS

A rapid, accurate and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS) method was established to determine LEV plasma concentrations. In this study, the levetiracetam plasma concentration monitoring data from 352 samples (taken from 248 patients) were used to explore the relationship between levetiracetam dose, age, combined administration with other antiseizure medications in patients with epilepsy.

RESULTS

Age and combined administration emerged as important affecting factors for the correlation of LEV concentration and dose. The correlation between concentration and dose was better in monotherapy. Combined administration may affect LEV concentration, especially when LEV is combined with oxcarbazepine, which might decrease the LEV concentration.

CONCLUSION

These findings emphasize the need to monitor LEV routinely LEV, especially among children and older adults when other antiseizure comedications are prescribed in the treatment regimen. LEV TDM is a well-established tool for the management of patients with epilepsy.

Clinical Application of Pharmacokinetics to Appraise Adherence to Levetiracetam in Portuguese Epileptic Patients

Adherence to antiseizure drug treatment determines its effectiveness and safety, and consequently affects patients’ quality of life. Herein, we assessed adherence to levetiracetam in Portuguese patients with refractory epilepsy (n = 115), with resort to a pharmacokinetic drug monitoring approach. The pharmacokinetic parameters of levetiracetam in each patient were determined in steady-state while admitted to the hospital. Then, adherence was assessed by comparing the plasma concentration of the drug observed on the first day of hospitalization with the predicted plasma concentration, considering previously determined pharmacokinetic parameters. The rate of adherence was assessed according to gender, age, diagnosis, and antiseizure drug regimen. Among 115 enrolled patients, 49 (42.6%) were identified as non-adherent, 30 (26.1%) classified as under-consumers, and 19 (16.5%) as over-consumers. A relationship between adherence, daily dose and plasma concentrations was herein reported for the first time. Adherent patients received higher daily doses of levetiracetam [2500 (2000–3000) mg] than non-adherent over-consumers [1500 (1000–2000) mg] and non-adherent under-consumers [2000 (1500–3000) mg]. Higher average steady-state plasma concentrations of levetiracetam were found in non-adherent under-consumers [27.28 (15.33–36.36) mg/L], followed by adherent patients [22.05 (16.62–29.81) mg/L] and non-adherent over-consumers [17.50 (10.69–24.37) mg/L]. This study demonstrates that adherence (or lack thereof) influences the plasma concentrations of levetiracetam in steady-state and its pharmacological effects. Moreover, it emphasizes the importance of educating patients to encourage adherence to therapy. Otherwise, the risk of developing toxic and subtherapeutic concentrations is undeniable, compromising the therapeutic effect and safety of treatment.

Levetiracetam Therapeutic Drug Monitoring in a Large Cohort of Korean Epileptic Patients

Levetiracetam is a new antiepileptic drug (AED) used for treating and preventing partial or generalized seizures. The usefulness of levetiracetam therapeutic drug monitoring (TDM) is related to inter- or intra-individual pharmacokinetic variability, drug interactions, and patient noncompliance. We aimed to investigate the levetiracetam TDM status in Korean epilepsy patients. Serum trough levetiracetam concentrations were measured using liquid chromatography–tandem mass spectrometry in 710 samples from 550 patients. The median (range) daily and weight-adjusted levetiracetam doses were 1500 (20–5000) mg and 25.5 (3.03–133.0) mg/kg, respectively. Patients on levetiracetam monotherapy constituted only 19.5% of the population, while 30.1% were on co-medication with valproate and 56.0% with enzyme-inducing AEDs (EIAEDs). Observed levetiracetam concentrations were widely distributed, ranging 0.8–95 mg/L, with a median of 17.3 mg/L. Levetiracetam concentrations were therapeutic, supra-therapeutic, and sub-therapeutic in 58.5% (n = 393), 11.6% (n = 78), and 29.9% (n = 201) of samples, respectively. There was a strong correlation between weight-adjusted levetiracetam dosage and concentrations (ρ = 0.6896, p < 0.0001). In this large-scale clinical study, a large inter-individual difference in levetiracetam pharmacokinetics was observed, and levetiracetam concentrations were influenced by EIAEDs. For individual dose adjustments and monitoring compliance, routine levetiracetam TDM is needed in epilepsy patients.

Xanthotoxin enhances the anticonvulsant potency of levetiracetam and valproate in the 6-Hz corneal stimulation model in mice

Xanthotoxin (8-methoxypsoralen; XANT) is a furanocoumarin that has many biological properties, including antiepileptic activity. This study evaluated the effect of XANT on the ability of classical and novel antiepileptic drugs to prevent seizures evoked by the 6-Hz corneal stimulation-induced seizure model, which is thought to be an experimental model of psychomotor (limbic) seizures in humans. XANT (50 mg/kg, administered i.p.) significantly potentiated the anticonvulsant activity of levetiracetam and valproate, decreasing their median effective dose (ED₅₀ ) values from 19.37 to 2.83 mg/kg (P < 0.01) for levetiracetam and from 92.89 to 44.44 mg/kg (P < 0.05) for valproate. Neither XANT (50 mg/kg) alone nor its combination with the anticonvulsant drugs (at their ED₅₀ values from the 6-Hz test) affected motor coordination; skeletal muscular strength and long-term memory, as determined in the chimney; and grip strength and passive avoidance tests, respectively. Measurement of total brain antiepileptic drug concentrations revealed that XANT (50 mg/kg) had no impact on levetiracetam total brain concentrations, indicating the pharmacodynamic nature of interaction between these antiepileptic drugs in the mouse 6-Hz model. However, XANT (50 mg/kg, i.p.) significantly increased total brain concentrations of valproate (P < 0.01), indicating the pharmacokinetic nature of interactions between drugs. XANT in combination with levetiracetam exerts beneficial anticonvulsant pharmacodynamic interactions in the 6-Hz mouse psychomotor seizure model.

[Epilepsy in the aged : Challenges in diagnostics and treatment]

Epilepsy is the third most frequent neurological disorder in aged patients after stroke and dementia. The incidence of epilepsy increases with age with the highest rates in patients ≥ 65 years old. Due to demographic changes the number of aged patients with epilepsy is expected to increase further in the coming years. The leading cause of new onset epilepsy in aged patients is cerebrovascular disease followed by dementia. The recognition of seizures in aged patients is often delayed. Status epilepticus occurs more frequently in aged patients and is associated with a high mortality and morbidity. Antiepileptic drug (AED) treatment of aged patients is complicated by comorbidities and polypharmacy and AEDs with a low interaction profile and high tolerability should be selected. Levetiracetam and lamotrigine are the AEDs of choice due to low interactions and good tolerability.

Behavioral adverse events with brivaracetam, levetiracetam, perampanel, and topiramate: A systematic review

PURPOSE

To understand the currently available post-marketing real-world evidence of the incidences of and discontinuations due to the BAEs of irritability, anger, and aggression in people with epilepsy (PWE) treated with the anti-seizure medications (ASMs) brivaracetam (BRV), levetiracetam (LEV), perampanel (PER), and topiramate (TPM), as well as behavioral adverse events (BAEs) in PWE switching from LEV to BRV.

METHODS

A systematic review of published literature using the Cochrane Library, PubMed/MEDLINE, and Embase was performed to identify retrospective and prospective observational studies reporting the incidence of irritability, anger, or aggression with BRV, LEV, PER, or TPM in PWE. The incidences of these BAEs and the rates of discontinuation due to each were categorized by ASM, and where possible, weighted means were calculated but not statistically assessed. Behavioral and psychiatric adverse events in PWE switching from LEV to BRV were summarized descriptively.

RESULTS

A total of 1500 records were identified in the searches. Of these, 44 published articles reporting 42 studies met the study criteria and were included in the data synthesis, 7 studies were identified in the clinical trial database, and 5 studies included PWE switching from LEV to BRV. Studies included a variety of methods, study populations, and definitions of BAEs. While a wide range of results was reported across studies, weighted mean incidences were 5.6% for BRV, 9.9% for LEV, 12.3% for PER, and 3.1% for TPM for irritability; 3.3%* for BRV, 2.5% for LEV, 2.0% for PER, and 0.2%* for TPM for anger; and 2.5% for BRV, 2.6% for LEV, 4.4% for PER, and 0.5%* for TPM for aggression. Weighted mean discontinuation rates were 0.8%* for BRV, 3.4% for LEV, 3.0% for PER, and 2.2% for TPM for irritability and 0.8%* for BRV, 2.4% for LEV, 9.2% for PER, and 1.2%* for TPM for aggression. There were no discontinuations for anger. Switching from LEV to BRV led to improvement in BAEs in 33.3% to 83.0% of patients (weighted mean, 66.6%). *Denotes only 1 study.

CONCLUSIONS

This systematic review characterizes the incidences of irritability, anger, and aggression with BRV, LEV, PER, and TPM, and it provides robust real-world evidence demonstrating that switching from LEV to BRV may improve BAEs. While additional data remain valuable due to differences in methodology (which make comparisons difficult), these results improve understanding of the real-world incidences of discontinuations due to these BAEs in clinical practice and can aid in discussions and treatment decision-making with PWE.

Is the anticonvulsant activity of levetiracetam dose-dependent?

PURPOSE

Although levetiracetam (LEV) is globally established as a leading antiseizure medication (ASM) it is still a controversial matter whether dose increases correspond with an increased efficacy if LEV in the recommended dose range did not show satisfying efficacy. In our clinical perception we questioned the value of dose increases in such non-responders.

METHODS

In this retrospective monocenter study we analyzed the data of adult people with epilepsies (PWE) with focal-onset seizures who had been treated at the department of adults of the Kork Epilepsy Center between 2009 and 2019, who had been on a stable daily LEV dose and in whom LEV was further increased due to further seizures in spite of baseline LEV in a recommended daily dose range. For reasons of data homogeneity, we included only PWE with at least two definite seizures during the hospital stay under the baseline LEV dose who were treated and observed as in-patients after the increase of LEV for a period at least three-fold longer than the baseline interval before. Additional data acquisition comprised clinical data including adverse events, serum concentrations of LEV and other ASMs, and additional laboratory findings. The primary outcome variable was the change of seizure frequency prior to and after the increase of LEV.

RESULTS

Out of 518 PWE who had been on LEV during their hospital stay, a total of 61 PWE fulfilled the inclusion criteria. After a gradual dose increment, 91,8 % of PWE showed a reduced seizure frequency, 73,8 % had a reduction of seizures of 50 % or more, and 21,3 % were seizure-free during the observation period. A significant seizure reduction could be shown with a seizure count of 2,5/week prior to the increment and 0,7/week after dose increment (p < 0,00001). Seven PWE reported minor adverse events and ten PWE showed slight laboratory changes (within normal levels).

CONCLUSION

Contrary to our long-term clinical impression, LEV dose increments were reasonable and improved the seizure situation in PWE, usually without additional safety hazards.

Prediction of Clearance in Children from Adults Following Drug-Drug Interaction Studies: Application of Age-Dependent Exponent Model

Background and Objective

Pharmacokinetic drug–drug interaction (DDI) studies are conducted in adult subjects during drug development but there are limited studies that have characterized pharmacokinetic DDI studies in children. The objective of this study was to evaluate if the DDI clearance values from adults can be allometrically extrapolated from adults to children.

Methods

Fifteen drugs were included in this study and the age of the children ranged from premature neonates to adolescents (30 observations across the age groups). The age-dependent exponent (ADE) model was used to predict the clearance of drugs in children from adults following DDI studies.

Results

The prediction error of drug clearances following DDIs in children ranged from 4 to 67%. Of 30 observations, 17 (57%) and 27 (90%) observations had a prediction error ≤ 30% and ≤ 50%, respectively.

Conclusion

This study indicates that it is possible to predict the clearance of drugs with reasonable accuracy in children from adults following DDI studies using an ADE model. The method is simple, robust, and reliable and can replace other complex empirical models.

Population Pharmacokinetics and Dosing Recommendations of Levetiracetam in Adult and Elderly Patients With Epilepsy

The objective was to develop and externally validate a population pharmacokinetic model of levetiracetam in adult and elderly patients with epilepsy, and to perform dosing simulations to propose individualized dosing regimens more likely to achieve therapeutic concentrations. This prospective study included 367 plasma samples from 107 patients receiving oral levetiracetam. Samples were analyzed by HPLC-UV. Pharmacokinetic data, as well as patient demographic, clinical characteristics, other drug therapy, and the use of innovator or generic products of levetiracetam, were collected. Population modeling was performed with NONMEM and included internal and external validations of the final model. Simulations were used to propose optimized dosing regimens. The pharmacokinetics of levetiracetam was described by a one-compartment model with first-order absorption and linear elimination. Body surface area had a significant effect on the apparent volume of distribution, as did creatinine clearance (CrCL) over the drug clearance (p < 0.01). The final model performed adequately during external validation testing. The final model showed a better predictive performance. Dosing simulations support 1000 mg 12-hourly dosing of levetiracetam for patients with CrCL ~60-75 mL/min with higher dose needed for higher values (1500 mg 12-hourly for CrCL ~93-111 mL/min). Dosing regimens should be personalized to the patient's CrCL to maximize the likelihood of therapeutic concentrations.

Clinical Impact of Co-medication of Levetiracetam and Clobazam with Proton Pump Inhibitors: A Drug Interaction Study

BACKGROUND

Clobazam (CLBZ) metabolized primarily by Cytochrome P-450 isoenzyme CYP3A4 than with CYP2C19, Whereas Levetiracetam (LEV) is metabolized by hydrolysis of the acetamide group. Few CYP enzymes are inhibited by Proton Pump Inhibitors (PPIs) Pantoprazole, Esomeprazole, and Rabeprazole in different extents that could affect drug concentrations in blood. The aim of the present study was to evaluate the effect of these PPIs on the plasma concentrations of LEV and CLBZ.

METHODS

Blood samples from 542 patients were included out of which 343 were male and 199 were female patients and were categorized as control and test. Plasma samples analyzed using an HPLC-UV method. Plasma concentrations were measured and compared to those treated and those not treated with PPIs. One way ANOVA and games Howell post hoc test used by SPSS 20 software.

RESULTS

CLBZ concentrations were significantly 10 folds higher in patients treated with Pantoprazole (P=0.000) and 07 folds higher in patients treated with Esmoprazole and Rabeprazole (P=0.00). Whereas plasma concentration of LEV control group has no statistical and significant difference when compared to pantoprazole (P=0.546) and with rabeprazole and esomeprazole was P=0.999.

CONCLUSION

The effect of comedication with PPIs on the plasma concentration of clobazam is more pronounced for pantoprazole to a greater extent when compared to esomeprazole and rabeprazole. When pantoprazole is used in combination with clobazam, dose reduction of clobazam should be considered, or significance of PPIs is seen to avoid adverse effects.

Pharmacological Management of the Genetic Generalised Epilepsies in Adolescents and Adults

Common genetic generalised epilepsy syndromes encountered by clinicians include childhood and juvenile absence epilepsies, juvenile myoclonic epilepsy and generalised tonic-clonic seizures on awakening. Treatment of these syndromes involves largely the use of broad-spectrum antiseizure drugs. Those effective for the generalised epilepsies include sodium valproate, phenobarbital, ethosuximide, clobazam, clonazepam, lamotrigine, levetiracetam, topiramate, zonisamide and, more recently, perampanel and brivaracetam. Results from the few rigorous studies comparing outcomes with drugs for genetic generalised epilepsies show valproate to be the most effective. The majority of patients with genetic generalised epilepsy syndromes will become seizure free on antiseizure monotherapy; those for whom control proves elusive may benefit from combination regimens. Early counselling regarding management may assist the patient to come to terms with their diagnosis and improve long-term outcomes. Treatment can be lifelong in some individuals, although others may remain seizure free without medication. Choice of antiseizure medication depends on the efficacy for specific seizure types, as well as tolerability. For patients prescribed comedication, drug interactions should be considered. In particular, for young women taking oral hormonal contraceptives, ≥ 200 mg/day of topiramate can decrease the circulating concentration of ethinylestradiol and ≥ 12 mg/day of perampanel can induce levonorgestrel metabolism. The use of valproate in women of childbearing potential is limited by associated teratogenic and neurodevelopmental effects in offspring. Given that valproate is often the antiseizure drug of choice for genetic generalised epilepsies, this creates a dilemma for patients and clinicians. Decision making can be aided by comprehensive assessment and discussion of treatment options. Psychiatric comorbidities are common in adolescents and adults with genetic generalised epilepsies. These worsen the prognosis, both in terms of seizure control and quality of life. Attendant lifestyle issues can impact significantly on the individual and society. Frontal lobe dysfunction, which can present in patients with juvenile myoclonic epilepsy, can adversely affect the long-term outlook, regardless of the nature of seizure control. Ongoing management requires consideration of psychosocial and behavioural factors that can complicate diagnosis and treatment. An assured supportive attitude by the neurologist can be an important contributor to a positive outcome. The mechanisms underlying genetic generalised epilepsies, including genetic abnormalities, are unclear at present. As the pathophysiology is unravelled, this may lead to the development of novel therapies and improved outcomes for patients with these syndromes.

Seizure Prophylaxis in Traumatic Brain Injury: A Comparative Study of Levetiracetam and Phenytoin Cerebrospinal Fluid Levels in Trauma Patients with Signs of Increased Intracranial Pressure Requiring Ventriculostomy

Background

One of the most common life-threatening injuries to trauma patients arriving in the emergency department (ED) is traumatic brain injury (TBI). Traditionally, intravenous medications have been given as seizure prophylaxis in patients demonstrating signs of increased intracranial pressure (ICP), as post-traumatic seizures in trauma patients are associated with higher morbidity and mortality. Medications traditionally given for this indication such as phenytoin have been established to reach therapeutic levels in the cerebrospinal fluid (CSF) quickly and are effective in preventing post-traumatic seizures but often have a large side-effect profile. A newer medication that is being used for seizure prophylaxis in patients with epilepsy is levetiracetam. Levetiracetam typically has a better side effect profile, but it has not been demonstrated that the drug reaches therapeutic levels in the CSF as quickly as phenytoin. Studies have shown levetiracetam and phenytoin to be equivocal in the prevention of post-TBI seizure prophylaxis.

Methods

This was a prospective, randomized, case-control study at a Level II trauma center of adult patients (age >/= 18 years) who suffered severe TBI (sTBI) requiring the placement of an external ventricular drain (EVD) from May 2017 to June 2018. Twelve patients were randomly placed into one of two groups for the administration of antiepileptic medication (either levetiracetam or phenytoin), allowing for the subsequent serial collection of CSF for the analysis of therapeutic levels of antiepileptic medications. Levetiracetam or phenytoin was administered at standardized fixed doses per our neurosurgical center standard protocol. CSF was collected before either drug was administered, 60 minutes after completion of administration and 360 minutes after completion of drug administration. Data analysis was performed to compare the time frame for which therapeutic levels of the medications were achieved in the CSF. The published steady-state and therapeutic CSF level of levetiracetam is 32 mcg/ml and phenytoin is 2 mcg/ml.

Results

A trend was observed in which the closer the fixed dosage approximated the weight-based dosing of phenytoin, the more their CSF phenytoin level increased (and approximated the therapeutic range) with an associated R-squared value of 0.6274. This trend was not found in patients receiving levetiracetam.

Conclusions

Levetiracetam does not reach levels needed for seizure prophylaxis in human CSF when loaded at standard dosing regimens in the acute setting. Phenytoin does reach levels needed for seizure prophylaxis in human CSF with standardized regimen dosing when dosages approximate weight-based dosing. If needed, in the acute setting phenytoin should have additional doses given prior to six hours after the loading dose to achieve therapeutic CSF levels. 

Levetiracetam

A comprehensive profile of levetiracetam is presented in this chapter which includes its description, formula, elemental analysis, appearance, uses and applications. Different earlier studies included for example methods of synthesis are described with its typical structural schemes. The profile also listed the drug's physical characteristics indicating its solubility, X-ray powder diffraction pattern, thermal methods of analysis as well as its spectroscopic characteristics. Different methods of analysis which includes compendial method of analysis, as well as reported method of analysis which include spectrophotometry, spectrofluorometry, electrochemical method, chromatographic method, and immunoassay method of analysis. The study was include drug stability, clinical pharmacology, e.g., mechanism of action, pharmacokinetic study. Around 70 references are recorded as a proof of this chapter.

Adverse Events of Antiepileptic Drugs Using Indonesian Version of Liverpool Adverse Events Profile

Introduction

Adverse events (AEs) associated with antiepileptic drugs (AEDs) affect people with epilepsy's (PWE) quality of life. A study conducted in 15 European countries showed that the AEs prevalence of AEDs in PWE was up to 80%. To date, there are no validated screening instruments to detect AEs of AEDs in Indonesian PWE. Therefore its epidemiology is currently unknown. This study aimed to validate the Indonesian version of Liverpool Adverse Events Profile (LAEP), consequently increasing physicians' awareness toward the probability of AEs and its necessary evaluation. Furthermore, this study was intended to determine the AEs prevalence of AEDs in Indonesian PWE.

Methods

The questionnaire was translated from English into Indonesian version. The validity and reliability were tested using Spearman correlation and Cronbach's alpha measurement. An observational cross-sectional study was carried out on consecutive PWE in outpatient clinic, Cipto Mangunkusumo Hospital. We analyzed duration of epilepsy, onset of epilepsy, seizure frequency, type of epilepsy, etiology and epilepsy syndrome, number of AEDs, duration of AED use, and comorbidity.

Results

All of the 19 items in the questionnaire were valid, with correlation coefficient ranging from 0.465 to 0.690 (moderate-strong correlation). Cronbach's alpha value was 0.846 (good consistency). The total of 90 subjects were enrolled with 91% screened as having AEs using LAEP questionnaire. The most common AEs were tiredness (67.8%), sleepiness (66.7%), memory problems (62.2%), and difficulty in concentrating (56.7%). The only clinical variable that influenced AEs was polytherapy.

Conclusion

The Indonesian version of LAEP was a valid and reliable instrument to screen AE of AEDs in PWE. Almost all the subjects in this study were suspected having AEs. Polytherapy was the independent factor of AE.

Population Pharmacokinetic Modeling of Levetiracetam in Pediatric and Adult Patients With Epilepsy by Using Routinely Monitored Data

BACKGROUND

Levetiracetam, a second-generation antiepileptic drug, is frequently used for managing partial-onset seizures. About 70% of the administered dose is excreted in urine unchanged, and dosage adjustment is recommended based on the individual's renal function. In this study, a population pharmacokinetic model of levetiracetam was developed using routinely monitored serum concentration data for individualized levetiracetam therapy.

METHODS

Patients whose serum concentrations of levetiracetam at steady-state were routinely monitored at Kyoto University Hospital from April 2012 to March 2013 were enrolled. The influence of patient characteristics on levetiracetam pharmacokinetics was evaluated using the nonlinear mixed-effects modeling (NONMEM) program.

RESULTS

A total of 583 steady-state concentrations from 225 patients were used for the analysis. The median patient age and estimated glomerular filtration rate (eGFR) were 38 (range: 1-89) years and 98 (15-189) mL·min·1.73 m, respectively. Serum concentration-time data of levetiracetam were well described by a 1-compartment model with first-order absorption. Oral clearance was allometrically related to the individual body weight and eGFR. An increase in the dose significantly increased oral clearance. No improvement in model fit was observed by including the covariate of any concomitant antiepileptic drugs. The population mean clearance for an adult weighing 70 kg and with a normal renal function was 4.8 and 5.9 L/h for 500 mg bis in die (bid) and 1500 mg bid, respectively.

CONCLUSIONS

Oral clearance allometrically related with body weight and eGFR can well predict the routine therapeutic drug monitoring data from pediatric to aged patients with varying renal function. Dosage adjustments based on renal function are effective in controlling the trough and peak concentrations in similar ranges.

A randomized, double-blind, placebo-controlled crossover study of the effects of levetiracetam on cognition, mood, and balance in healthy older adults

OBJECTIVE

The cognitive and mood effects of levetiracetam (LEV) in older adults are not known. This study compared the cognitive and mood effects of LEV to placebo in healthy older adults.

METHODS

Cognitive, mood, and balance variables were compared between LEV and placebo using a randomized, double-blind, placebo-controlled crossover study with two 5-week treatment periods. Healthy volunteers (n = 20) aged 65-80 (mean age 72.4) received either LEV or placebo in which the LEV target dose was 1,000 mg/day. Volunteers, aged 65-80, were without epilepsy to limit potentially confounding the impact of seizures and/or underlying neuropathology on outcomes. LEV was initiated at 250 mg twice a day for 2 weeks, then increased to 500 mg twice a day for 2 weeks, and then tapered to 250 mg twice a day for 1 week. This was randomized with placebo for the two treatment arms. Measures included standardized neuropsychological, mood, and balance tests yielding 32 variables. Balance was assessed using subjective report (e.g., A-B neurotoxicity scale) and objective data (e.g., Berg Balance Scale).

RESULTS

Average LEV serum concentration was 16.9 (standard deviation [SD} 7.7). Repeated-measures analysis of variance (ANOVA) found no differences between LEV and placebo phases for 29 (90.6%) of 32 variables including no change in balance. Performance on LEV was better than placebo on a visual memory (MCG Complex Figure Recall; p = 0.007) and two attention tests (Trail Making Test, Part A, p = 0.009; Stroop Interference, p = 0.004). There was a trend for greater irritability and fatigue (POMS Anger and Fatigue) during the LEV phase (p = 0.029, p = 0.035). Effect-size changes were generally small (Cohen d < 0.5).

SIGNIFICANCE

LEV was well tolerated in this elderly population in terms of cognition, mood, and balance. When anticonvulsant medication is indicated for older adults, LEV has pharmacokinetic advantages, and these data indicate no adverse impact on cognition or balance.

An Analytical Study to Correlate Serum Levels of Levetiracetam with Clinical Course in Patients with Epilepsy

Introduction:

With the advancement of therapeutics, newer antiepileptic drugs (AEDs) like Levetiracetam (LEV), with good therapeutic efficacy and tolerability are available. But unfortunately, therapeutic drug monitoring is not routinely done in India for these drugs.

Objectives:

The objective of this study is to determine the range of serum levels of LEV in patients at stabilized doses and correlate them with their clinical course.

Materials and Methods:

Patients with epilepsy and started on LEV were enrolled from the Neurology Department after the Ethics Committee approval. Serum levels of LEV were estimated using high-performance liquid chromatography and correlated with patient demographics, dosage, dosage forms, concomitant AEDs, compliance of the patient, therapeutic effect, adverse drug reactions (ADRs), and suspected toxicity.

Results:

Serum levels of LEV ranged from 0.4 to 102.2 μg/ml at different time points and demonstrated a negligible positive correlation with age of the patients (r = 0.12) but negligible negative correlation with bodyweight (r = −0.19). No conclusive relationship could be established for dose, gender, dosage forms, clinical efficacy (seizure frequency), ADRs, and toxicity. Compliance was verified in all the patients. Levels were found to reduce with the use of concomitant enzyme inducer drugs (56.78%) whereas increase with valproic acid (7.8%).

Conclusion:

These findings emphasize the need for monitoring the serum levels of newer AEDs like LEV considering the various parameters studied here, so as to maintain the therapeutic efficacy by preventing under or over dosage and to generate a broader database of serum levels of LEV in the Indian population to help appropriate prescribing with more confidence.

Drug-resistant epilepsy in adults: Outcome trajectories after failure of two medications

OBJECTIVE

To examine the seizure trajectories of adults with epilepsy developing drug-resistant epilepsy (DRE) and to identify the predictors of seizure trajectory outcome.

METHODS

Adult patients failing two antiepileptic drugs (AEDs) due to inefficacy and starting their third AED at a tertiary epilepsy center were followed for seizure trajectory outcome during medical management. Seizure trajectories were categorized into one of four patterns: (1) course with constant seizures; (2) fluctuating course; (3) delayed attainment of seizure freedom (seizure freedom delayed for >12 months after start of the study, but patient stayed in seizure freedom); and (4) early attainment of seizure freedom (within 12 months of starting study). Multiple ordinal logistic regression models were used to estimate the association between trajectory categories and clinical factors.

RESULTS

Four hundred three adult patients met the eligibility criteria. Of these, 212 (53%) never achieved a seizure-free period of a year or more. The trajectories of 63 patients (16%) had a complex fluctuating trajectory, 62 (15%) had delayed onset of seizure freedom, and 66 (16%) had an early seizure freedom. Independent predictors associated with more favorable outcome trajectories were epilepsy type and length of follow-up. Specifically, compared to patients with focal epilepsy of temporal lobe, patients with focal epilepsy of occipital lobe (OR 3.80, 95% confidence interval [CI] 1.00-14.51, p = 0.04), generalized genetic (OR 3.23, 95% CI 1.88-5.57, p < 0.0001), unclear epilepsy type (OR 3.82, 95% CI 1.53-9.52, p < 0.005), and both focal and generalized epilepsy(OR 11.73, 95% CI 1.69-81.34, p = 0.01) were significantly more likely to experience a better trajectory pattern.

SIGNIFICANCE

Examination of patterns of seizure trajectory of patients with incident DRE showed that 31% were in continuous seizure freedom at the end of the observation period.

Development and validation of a HPLC-UV method for the quantification of antiepileptic drugs in dried plasma spots

BACKGROUND

Therapeutic drug monitoring (TDM) of antiepileptic drugs is widely used in clinical practice to optimise therapy, but it is limited by technical problems and cost considerations. The aim of the present study was: 1) to validate a chromatographic method for the concomitant determination of levetiracetam, lamotrigine, ethosuximide, felbamate, rufinamide, zonisamide and monohydroxycarbamazepine; 2) to develop it for dried plasma spot (DPS) assessing its reliability against the classical determination from plasma; and 3) test its clinical application.

METHODS

Extraction of plasma samples and DPS was done by simple precipitation. Chromatographic analysis was performed using high performance liquid chromatography with ultraviolet detection. After validation, both methods were applied for the quantification of plasma samples from patients on antiepileptic therapy.

RESULTS

Mean inter- and intra-day accuracy and precision were <15% for all compounds both in plasma and in DPS samples. DPS samples were considered stable under tested conditions. Measurements between plasma and DPS samples appeared related (p<0.0001). Bland-Altman analysis revealed accordance in lamotrigine values with mean overestimation of concentration for DPS sample of 2.8%. Also for monohydroxycarbamazepine data the agreement was acceptable (mean overestimation of 9.2%). For levetiracetam mean difference was 7.6%, while for ethosuximide mean percentage difference was 20.6%.

CONCLUSIONS

The developed methods simplify TDM of antiepileptic drugs. This is particularly relevant for the method on dried spot sample devices because it facilitates further sample handling, stability and shipments making the management of therapies in epileptic patients easier also in hospitals devoid of a dedicated laboratory.

Lacosamide serum concentrations in adult patients with epilepsy: the influence of gender, age, dose, and concomitant antiepileptic drugs

OBJECTIVE

Lacosamide (LCM), a new antiepileptic drug (AED) approved as adjunctive therapy for the treatment of patients with partial-onset seizures, has limited pharmacokinetic and drug interaction data. The main objectives of the present study were to investigate the effects of dose, age, gender, and hepatic enzyme-inducing AEDs on the pharmacokinetics of LCM as assessed by steady state serum LCM values.

METHODS

An LCM AED therapeutic drug monitoring database was analyzed with regard to LCM serum concentrations and other relevant patient and AED drug information. One hundred twenty eight sera were identified. These were collected from 68 women and 61 men aged 19-66 years, who were prescribed a median LCM dose of 300 mg (range 50-600 mg).

RESULTS

Serum LCM concentrations were observed in the following main groupings: LCM monotherapy (n = 5), LCM with nonenzyme-inducing AEDs (n = 50), LCM with enzyme-inducing AEDs (n = 49), LCM with valproic acid (n = 20), and LCM with enzyme-inducing AEDs plus valproic acid (n = 4). Analysis of variance showed a correlation of dose with LCM concentrations (r = 0.53, P < 0.001), and women had statistically higher mean LCM concentration than did men, 37.2 ± 23.6 versus 26.8 ± 12.9 μmol/L (P = 0.001). Serum LCM concentrations were significantly lower (P = 0.002) in the enzyme-inducing AED group (carbamazepine and phenytoin) compared with the LCM monotherapy group and the nonenzyme-inducing group, 23.5 ± 11.0, 34.5 ± 7.7, and 32.7 ± 17.9 μmol/L, respectively.

CONCLUSIONS

Serum LCM concentrations increased dose dependently, were age independent, and were higher in women compared with men. Carbamazepine and phenytoin can significantly decrease serum LCM concentrations, probably via induction of LCM metabolism.

Effect of chronic administration of phenobarbital, or bromide, on pharmacokinetics of levetiracetam in dogs with epilepsy

BACKGROUND

Levetiracetam (LEV) is a common add-on antiepileptic drug (AED) in dogs with refractory seizures. Concurrent phenobarbital administration alters the disposition of LEV in healthy dogs.

HYPOTHESIS/OBJECTIVES

To evaluate the pharmacokinetics of LEV in dogs with epilepsy when administered concurrently with conventional AEDs.

ANIMALS

Eighteen client-owned dogs on maintenance treatment with LEV and phenobarbital (PB group, n = 6), LEV and bromide (BR group, n = 6) or LEV, phenobarbital and bromide (PB-BR group, n = 6).

METHODS

Prospective pharmacokinetic study. Blood samples were collected at 0, 1, 2, 4, and 6 hours after LEV administration. Plasma LEV concentrations were determined by high-pressure liquid chromatography. To account for dose differences among dogs, LEV concentrations were normalized to the mean study dose (26.4 mg/kg). Pharmacokinetic analysis was performed on adjusted concentrations, using a noncompartmental method, and area-under-the-curve (AUC) calculated to the last measured time point.

RESULTS

Compared to the PB and PB-BR groups, the BR group had significantly higher peak concentration (Cmax ) (73.4 ± 24.0 versus 37.5 ± 13.7 and 26.5 ± 8.96 μg/mL, respectively, P < .001) and AUC (329 ± 114 versus 140 ± 64.7 and 98.7 ± 42.2 h*μg/mL, respectively, P < .001), and significantly lower clearance (CL/F) (71.8 ± 22.1 versus 187 ± 81.9 and 269 ± 127 mL/h/kg, respectively, P = .028).

CONCLUSIONS AND CLINICAL IMPORTANCE

Concurrent administration of PB alone or in combination with bromide increases LEV clearance in epileptic dogs compared to concurrent administration of bromide alone. Dosage increases might be indicated when utilizing LEV as add-on treatment with phenobarbital in dogs.

Measurement of levetiracetam drug levels to assist with seizure control and monitoring of drug interactions with other anti-epileptic medications (AEMs)

PURPOSE

Levetiracetam (LEV) therapeutic range (20-40mg/L) and potential drug interactions were assessed in people with epilepsy (PWE).

METHOD

Fifty-two PWE had LEV and concomitant medications [carbamazepine (CBZ); valproate (VPA); lamotrigine (LTG)] blood levels measured and compared to seizure activity. Lacosamide (LCM) levels were unavailable. Adopted therapeutic ranges were: 20-40mg/L - LEV; 25-50μmol/L - total CBZ; 6-13μmol/L - free CBZ; 300-750μmol/L - total VPA; 30-75μmol/L - free VPA; and 40-60μmol/L - LTG. Seizure-freedom was assessed and patients followed for almost two years.

RESULTS

23 of 52 PWE (44%) used LEV monotherapy and 16/23 (70%) had 'therapeutic' LEV with 13/16 (81%) seizure-free. 29 of 52 (56%) used polytherapy and 16/29 (55%) had 'therapeutic' LEV with 7/16 (44%) seizure-free. 11 of 29 (38%) used CBZ: 4/11 (36%) had therapeutic mean LEV levels and 7/11 (64%) were seizure-free. Fourteen (48%) used VPA: 9/14 (64%) had therapeutic mean LEV levels and 8/14 (57%) were seizure-free. 13 of 29 (45%) used LTG: 8/13 (62%) had therapeutic mean LEV levels and 5/13 (38%) were seizure-free. LEV did not alter CBZ, but CBZ affected LEV. LEV elevated VPA free levels but not VPA total levels. Dosage/concentration was lowered with polytherapy.

CONCLUSION

LEV range (20-40mg/L) assisted epilepsy management and anti-epileptic medication interactions were suggested with polytherapy thus possibly explaining the impaired efficacy of LEV with polytherapy.

Clinical pharmacokinetics of new-generation antiepileptic drugs at the extremes of age: an update

Epilepsies occur across the entire age range, and their incidence peaks in the first years of life and in the elderly. Therefore, antiepileptic drugs (AEDs) are commonly used at the extremes of age. Rational prescribing in these age groups requires not only an understanding of the drugs' pharmacodynamic properties, but also careful consideration of potential age-related changes in their pharmacokinetic profile. The present article, which updates a review published in 2006 in this journal, focuses on recent findings on the pharmacokinetics of new-generation AEDs in neonates, infants, children, and the elderly. Significant new information on the pharmacokinetics of new AEDs in the perinatal period has been acquired, particularly for lamotrigine and levetiracetam. As a result of slow maturation of the enzymes involved in glucuronide conjugation, lamotrigine elimination occurs at a particularly slow rate in neonates, and becomes gradually more efficient during the first months of life. In the case of levetiracetam, elimination occurs primarily by renal excretion and is also slow at birth, but drug clearance increases rapidly thereafter and can even double within 1 week. In general, infants older than 2-3 months and children show higher drug clearance (normalized for body weight) than adults. This pattern was confirmed in recent studies that investigated the pediatric pharmacokinetics of several new AEDs, including levetiracetam, rufinamide, stiripentol, and eslicarbazepine acetate. At the other extreme of age, in the elderly, drug clearance is generally reduced compared with younger adults because of less efficient drug-metabolizing activity, decreased renal function, or both. This general pattern, described previously for several AEDs, was confirmed in recent studies on the effect of old age on the clearance of felbamate, levetiracetam, pregabalin, lacosamide, and retigabine. For those drugs which are predominantly eliminated by renal excretion, aging-related pharmacokinetic changes could be predicted by measuring creatinine clearance (CLCR). Overall, most recent findings confirm that age is a major factor influencing the pharmacokinetic profile of AEDs. However, pharmacokinetic variability at any age can be considerable, and the importance of other factors should not be disregarded. These include genetic factors, co-morbidities, and drug interactions, particularly those caused by concomitantly administered AEDs which induce or inhibit drug-metabolizing enzymes.

Pharmacokinetic variability of four newer antiepileptic drugs, lamotrigine, levetiracetam, oxcarbazepine, and topiramate: a comparison of the impact of age and comedication

BACKGROUND

Newer antiepileptic drugs (AEDs) are widely used in patients with epilepsy. There is still insufficient documentation regarding pharmacokinetic variability of these AEDs in different patient groups.

PURPOSE

The purpose of this study was to compare age and comedication as factors contributing to pharmacokinetic variability between 4 newer AEDs (lamotrigine, levetiracetam, oxcarbazepine, and topiramate) among patients with refractory epilepsy.

METHODS

Data regarding age, gender, use of AEDs, daily doses, and serum concentration measurements were retrieved from a therapeutic drug monitoring database, from patients admitted to the National Center for Epilepsy, Norway, 2007-2008.

RESULTS

In total, 1050 patients were included, 111 younger children (2-9 years), 137 older children (10-17 years), 720 adults (18-64 years), 82 elderly (65-93 years). Fifty percent of the patients were prescribed polytherapy, in 88 different combinations. The interindividual pharmacokinetic variability was extensive, as illustrated by a 10-fold variability in serum concentration compared with dose. Age affected the apparent clearance of levetiracetam to the largest extent, as shown by a 60% increase in younger children and a 40% reduction in the elderly, respectively, compared with adults. Comedication altered the clearance of lamotrigine to the greatest extent ±70% because it is affected by both enzyme inducers and inhibitors. Hepatic enzyme inducers increased the clearance of levetiracetam and topiramate by 25% and oxcarbazepine by 75%. Valproic acid reduced the clearance of topiramate by 25%.

CONCLUSION

Age and comedication are important contributors to pharmacokinetic variability. Age had the greatest impact on levetiracetam, and comedication affected the clearance of each of the 4 AEDs investigated in this study. Pharmacokinetic drug interactions must be carefully considered when multidrug therapies are prescribed. Therapeutic drug monitoring is a valuable tool for individualizing AED therapy.

Safety and efficacy of levetiracetam for the treatment of partial onset seizures in children from one month of age

Epilepsy is a common neurological disorder in the pediatric population, affecting up to one percent of children, and for which the mainstay of treatment is anticonvulsant medication. Despite the frequent use of anticonvulsant drugs, remarkably little is known about the safety and efficacy of most of these medications in the pediatric epilepsy population. Of 34 anticonvulsants currently approved for use by the US Food and Drug Administration (FDA), only 13 have been approved for use in children. Although infants and young children are disproportionately affected by epilepsy, there are currently only three anticonvulsant medications that have been specifically evaluated and approved for use in children younger than 2 years of age. In 2012, the FDA approved levetiracetam as an adjunctive treatment for partial onset seizures in infants and children from one month of age. Here we review the available data on levetiracetam in the pediatric epilepsy population. We first discuss the pharmacological profile of levetiracetam, including its mechanism of action, formulations and dosing, and pharmacokinetics in children. We then review the available efficacy, safety, and tolerability data in children from one month of age with partial onset seizures. We conclude that the current data leading to the approval of levetiracetam for use in infants and children with partial onset seizures is encouraging, although more work needs to be done before definitive conclusions can be drawn about the efficacy of levetiracetam across different pediatric age groups.

Host factors affecting antiepileptic drug delivery-pharmacokinetic variability

Antiepileptic drugs (AEDs) are the mainstay in the treatment of epilepsy, one of the most common serious chronic neurological disorders. AEDs display extensive pharmacological variability between and within patients, and a major determinant of differences in response to treatment is pharmacokinetic variability. Host factors affecting AED delivery may be defined as the pharmacokinetic characteristics that determine the AED delivery to the site of action, the epileptic focus. Individual differences may occur in absorption, distribution, metabolism and excretion. These differences can be determined by genetic factors including gender and ethnicity, but the pharmacokinetics of AEDs can also be affected by age, specific physiological states in life, such as pregnancy, or pathological conditions including hepatic and renal insufficiency. Pharmacokinetic interactions with other drugs are another important source of variability in response to AEDs. Pharmacokinetic characteristics of the presently available AEDs are discussed in this review as well as their clinical implications.

Serum concentrations of rufinamide in children and adults with epilepsy: the influence of dose, age, and comedication

Rufinamide (RUF) is an orphan drug for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in persons aged 4 years and older. Several studies have investigated the pharmaconkinetics of RUF, but information about interactions is still limited and the results are in part inconsistent. The aim of our study was to analyze the effect of age, gender, daily RUF dose per body weight (mg/kg), valproic acid (VPA), and enzyme-inducing antiepileptic drugs (EIAEDs) on RUF concentration-to-dose ratio (RUF serum concentration/RUF dose per body weight), RUF clearance (RUF dose/RUF serum concentration), and RUF trough concentrations. Different statistical methods were used to evaluate 292 blood samples from 119 patients who fulfilled the inclusion criteria. In summary, the results using generalized estimating equation regression models confirm a moderate but statistically significant nonlinear RUF concentration-dose relationship. At steady state, the trough concentrations of RUF increase in a less than dose proportional manner. Children (younger than 12 years) had significantly lower RUF concentrations (19.0%, P < 0.001) than adults (18 years or older) on comparable RUF doses per body weight. VPA was the most frequent comedication (51%) in our patient group. Mean RUF concentrations were 86.6% higher when VPA concentrations were greater than 90 μg/mL (P < 0.001) and 45.4% higher when VPA concentrations were between 50 and 90 μg/mL (P < 0.001) but not significantly different at VPA concentrations less than 50 μg/mL (4.4%, P > 0.1) compared with combinations without VPA. In combination with EIAEDs, mean RUF concentrations were 21.8% lower (P = 0.002) compared with combinations without EIAEDs. However, the group of AEDs classified as EIAEDs was heterogeneous and the number of patients, especially of children with EIAEDs, was relatively small. Our data indicate that oxcarbazepine and, especially, methsuximide decrease RUF concentrations as well. Therapeutic drug monitoring might be helpful because RUF concentrations differ markedly in patients on comparable RUF doses.

Levetiracetam: a review of its use in epilepsy

Levetiracetam (Keppra®, E Keppra®) is an established second-generation antiepileptic drug (AED). Worldwide, levetiracetam is most commonly approved as adjunctive treatment of partial onset seizures with or without secondary generalization; other approved indications include monotherapy treatment of partial onset seizures with or without secondary generalization, and adjunctive treatment of myoclonic seizures associated with juvenile myoclonic epilepsy and primary generalized tonic-clonic (GTC) seizures associated with idiopathic generalized epilepsy. Levetiracetam has a novel structure and unique mechanisms of action. Unlike other AEDs, the mechanisms of action of levetiracetam appear to involve neuronal binding to synaptic vesicle protein 2A, inhibiting calcium release from intraneuronal stores, opposing the activity of negative modulators of GABA- and glycin-gated currents and inhibiting excessive synchronized activity between neurons. In addition, levetiracetam inhibits N-type calcium channels. Levetiracetam is associated with rapid and complete absorption, high oral bioavailability, minimal metabolism that consists of hydrolysis of the acetamide group, and primarily renal elimination. It lacks cytochrome P450 isoenzyme-inducing potential and is not associated with clinically significant pharmacokinetic interactions with other drugs, including other AEDs. The efficacy of oral immediate-release levetiracetam in controlling seizures has been established in numerous randomized, double-blind, controlled, multicentre trials in patients with epilepsy. Adjunctive levetiracetam reduced the frequency of seizures in paediatric and adult patients with refractory partial onset seizures to a significantly greater extent than placebo. Monotherapy with levetiracetam was noninferior to that with carbamazepine controlled release in controlling seizures in patients with newly diagnosed partial onset seizures. Levetiracetam also provided seizure control relative to placebo as adjunctive therapy in patients with idiopathic generalized epilepsy with myoclonic seizures or GTC seizures. In addition, patients receiving oral levetiracetam showed improvements in measures of health-related quality of life relative to those receiving placebo. Although treatment-emergent adverse events were commonly reported in the clinical trials of levetiracetam, the overall proportion of patients who experienced at least one treatment-emergent adverse event was broadly similar in the levetiracetam and placebo treatment groups, with most events being mild to moderate in severity. Levetiracetam is not associated with cognitive impairment or drug-induced weight gain, but has been associated with behavioural adverse effects in some patients.

Antiepileptic drug interactions - principles and clinical implications

Antiepileptic drugs (AEDs) are widely used as long-term adjunctive therapy or as monotherapy in epilepsy and other indications and consist of a group of drugs that are highly susceptible to drug interactions. The purpose of the present review is to focus upon clinically relevant interactions where AEDs are involved and especially on pharmacokinetic interactions. The older AEDs are susceptible to cause induction (carbamazepine, phenobarbital, phenytoin, primidone) or inhibition (valproic acid), resulting in a decrease or increase, respectively, in the serum concentration of other AEDs, as well as other drug classes (anticoagulants, oral contraceptives, antidepressants, antipsychotics, antimicrobal drugs, antineoplastic drugs, and immunosupressants). Conversely, the serum concentrations of AEDs may be increased by enzyme inhibitors among antidepressants and antipsychotics, antimicrobal drugs (as macrolides or isoniazid) and decreased by other mechanisms as induction, reduced absorption or excretion (as oral contraceptives, cimetidine, probenicid and antacides). Pharmacokinetic interactions involving newer AEDs include the enzyme inhibitors felbamate, rufinamide, and stiripentol and the inducers oxcarbazepine and topiramate. Lamotrigine is affected by these drugs, older AEDs and other drug classes as oral contraceptives. Individual AED interactions may be divided into three levels depending on the clinical consequences of alterations in serum concentrations. This approach may point to interactions of specific importance, although it should be implemented with caution, as it is not meant to oversimplify fact matters. Level 1 involves serious clinical consequences, and the combination should be avoided. Level 2 usually implies cautiousness and possible dosage adjustments, as the combination may not be possible to avoid. Level 3 refers to interactions where dosage adjustments are usually not necessary. Updated knowledge regarding drug interactions is important to predict the potential for harmful or lacking effects involving AEDs.